We rode MS on its soft opening day---when it was, from what I understand, lots more intense. Everyone in my party (all adults) has mild motion sickness, but the opportunity to ride on the opening day was exciting!
I was a little dizzy but basically okay (thought the effects were pretty cool); my sister & my mom stumbled off the ride. We went into Universe of Energy, where my (very proper) mother plopped down on the floor because she "had to sit" (usually not allowed, but there were a number of people who appeared out of sorts on the floor, and the CMs were letting it go). I was seriously concerned about getting them back to the hotel as I was the only one with my wits about me, but after Universe of Energy, a pretzel (something else she "had to have" after the ride), and a little walking, everyone was better.
We all agree that we were glad we did it but don't ever really care to do it again.